Management of habitat diversity on arable farmland to maximise control of crop pestsby communities of beneficial organisms

Abstract: The effect of habitat diversity on beneficial insects is being assessed in order tooptimise the management of the arable landscape to improve pest suppression. The abundance ofaphids and their natural enemies was assessed by Vortis sampling on uncropped and cropped landwithin 100 ha study areas on twelve farms in the east of England. Eight of these farms hadadditional sown covers established on them, either as strips or blocks and in two quantities, 1.5and 6ha. All samples were taken in July 2008. The new covers comprised natural regeneration(NR), floristically enhanced grass (FEG), insect rich cover (IRC) and winter bird cover (WBC).Within the newly sown covers the total number of natural enemies was greatest in the FEG,although parasitoid numbers were greatest in the WBC in which flowering fodder radish provideda supply of nectar at that time. Although parasitoids were equally abundant in strips and blocks,the total number of natural enemies was greatest in strips, perhaps reflecting variability inmobility of different taxa. We hypothesised that the total number of natural enemies would begreater in the new sown habitats than in other uncropped land areas, but this was not the case in2008 and may have been because the covers were newly established that spring. Further datafrom 2009 and 2010 will aid interpretation. There were fewer aphids in crops on farms with theadditional sown covers compared to farms without additional covers. While we hypothesise thatthis could have been as a result of enhanced enemy activity prior to the date we sampled, andassociated with the presence of the experimental sown covers, we will only be able to understandthis more fully by evaluating additional through-season samples that were made on a sub-set ofthe farms and data from subsequent years. Here we have presented preliminary interpretationsbased on available data for 2008 only. Far more robust analysis and interpretation will be possiblewhen we are able to include data from 2009 and 2010.